1. Field of the Invention
The present invention relates to semiconductors, and in particular to a semiconductor device with a copper contact or interconnect having TaN barrier at minimal thickness and fabrications thereof.
2. Description of the Related Art
Electrically conductive lines providing, for example, signal transfer are essential in electronic devices as well as semiconductor integrated circuit (IC) devices. Electrically conductive lines on different levels are connected by electrically conductive plugs in required position, providing a predetermined function.
Recently, fabrication using copper has been introduced to solve problems such as RC delay caused by feature size reduction responding to demands for increased integrity. Moreover, copper shows better heat conductivity, providing better electromigration (EM) resistance than conventional aluminum. Copper fabrication compatible with low-k dielectric material has become a popular interconnect process.
Nevertherless, one disadvantage of the copper fabrication is diffusion of copper to adjacent dielectric material, affecting reliability of the IC device. A metal barrier layer comprising material such as tantalum (Ta) or tantalum nitride (TaN) is thus provided for diffusion suppression. However, the tantalum (Ta) or tantalum nitride (TaN) barrier is normally formed by PVD such as sputtering at a thickness exceeding 100 Å.
Due to the critical dimension (CD) reduction of semiconductor devices, copper contacts, such as copper contact plugs are required in the front-end fabrication to electrically contact the active regions formed on a semiconductor substrate or a gate electrode of a transistor. Hence, thinner and more reliable diffusion barriers are needed to prevent undesired copper diffusion.